Field of the Invention
The present invention relates to a method and equipment for controlling a manufacturing process of a component of a tire for vehicle wheels. More specifically, the invention relates to a control method and equipment for detecting deposition anomalies of a continuous elongated element in a manufacturing process of a component of a tire in which the continuous elongated element, fed by a supplying member, is placed on a forming support by means of at least one pressing member active on said continuous elongated element along an application direction.
Description of the Related Art
A tire for vehicle wheels typically comprises a carcass structure, shaped according to a substantially toroidal configuration, comprising at least one carcass ply having respectively opposite end portions. The latter are engaged with respective annular anchoring structures, each of them normally formed from at least one substantially circumferential annular insert called “bead core” on which at least one filling insert is generally applied, tapering radially going away from the rotation axis. The annular anchoring structures are arranged in areas usually identified by the term “beads”. The beads have an internal diameter substantially corresponding to a so-called “fitting-diameter” of the tire on a respective assembly rim.
The tire also comprises a crown structure comprising at least one belt strip arranged in a position radially outside the carcass ply with respect to the rotation axis of the tire and a tread band radially outside the belt strip. Longitudinal and transversal grooves are typically formed into the tread band, arranged to define a desired tread pattern. Between the tread band and the belt strip(s) there can be a so-called “under-layer” made of elastomeric material with suitable properties to ensure a stable connection of the belt strip(s) with the tread band itself.
The tire also comprises a pair of so-called sidewalls made from elastomeric material that represent the axially outer surfaces of the tire, with respect to a middle plane perpendicular to the rotation axis of the tire itself. For example, the sidewalls represent the axially outer surfaces with respect to the annular anchoring structures, to the carcass ply(-ies), to the belt strip(s) and possibly to at least one tread band portion.
In “tubeless” tires, there is, in a radially inner position with respect to the carcass ply, at least one layer of elastomeric material, usually called “liner”, having air-tightness characteristics and generally extending from one of the beads to the other.
The production cycles of a tire provide that, after a building process in which the various structural components of the tire itself are made and/or assembled, the built green tires are transferred into a molding and vulcanizing line where a molding and vulcanization process is carried out, adapted to define the structure of the tire according to a desired geometry and tread pattern.
In the present description and subsequent claims, by the term “elastomeric material” it is meant to indicate a composition comprising at least one elastomeric polymer and at least one reinforcing filler. Preferably, such a composition also comprises additives like, for example, a cross-linking agent and/or a plasticizer. Thanks to the presence of the cross-linking agent, such a material can be cross-linked by heating, so as to form the final manufactured product.
By the term “continuous elongated element” it is meant to indicate an element made from elastomeric material, preferably made without the use of reinforcing cords, in which the longitudinal dimensions are greater than the transversal dimensions and the thickness. Preferably, the continuous elongated element is directly fed through extrusion from a suitable draw-plate/extruder. Alternatively, the continuous elongated element is fed from a reel collecting the same, as obtained beforehand by drawing/extrusion.
By the term “structural component”, or simply “component” of a tire it is meant to indicate any component suitable for carrying out a function in the tire or a portion thereof, selected for example from: liner, under-liner, carcass ply(-ies), under-belt insert, crossed over or zero degrees belt strips, thin sheet for the tread band, tread band, bead core, bead filler, reinforcing inserts, made from textile, metallic or only elastomeric material, anti-abrasion insert, sidewall inserts.
By the term “application direction” it is meant to indicate the direction along which the force that keeps a pressing member pressed against a forming support acts. The terms “axial”, “axially”, “radial”, “radially”, “circumferential” and “circumferentially” are used with reference to the forming support.
In particular, by the terms “axial” and “axially” it is meant to indicate references/quantities arranged/measured or extending in a direction substantially parallel to the rotation axis of the forming support.
By the terms “radial” and “radially” it is meant to indicate references/quantities arranged/measured or extending in a direction substantially perpendicular to the rotation axis of the forming support, in other words in a direction that intersects the rotation axis of the forming support and lies in a plane comprising such a rotation axis.
By the terms “circumferential” and “circumferentially” it is meant to indicate references/quantities arranged/measured or extending in a direction parallel to a direction defined in any point of the forming support along the tangent to the forming support at that point and perpendicular to the axial direction and to the radial direction.
Conventional production processes of tires for vehicle wheels essentially provide that the components of the tire described above be pre-fabricated separately from one another, to then be assembled in a subsequent building step of the tire.
The current trend, however, is to use processes that make it possible to minimise or, possibly, eliminate the pre-fabrication and storage of such components.
More specifically, now process solutions are adopted that provide to build the single components of the tire directly onto a forming support, according to a predetermined sequence.
In WO 01/36185 to the same Applicant, the components of the tire are made on a toroidal support, by sequentially applying onto the latter a plurality of elongated elements, for example consisting of individual rubberized cords or of rubberized cords grouped in parallel in the form of strip-like elements, particularly used to make the carcass and belt structure, and continuous elongated elements made of elastomeric material, particularly used to make the other structural components of the tire like for example tread band, sidewalls, liner, fillers.
WO 2006/059351 to the same Applicant describes a method for controlling a manufacturing process of components of a tire for vehicle wheels in which an elongated element fed by a supplying member is distributed over a forming support by means of a pressing member active on the elongated element along a pressing direction. The method comprises the steps of: detecting, with a predetermined frequency, the instantaneous acceleration value of said pressing member along said pressing direction; comparing the detected value of said instantaneous acceleration with a threshold value; generating a warning signal when the detected value of said instantaneous acceleration exceeds said threshold value.
In cases of the type described in WO 01/36185 and WO 2006/059351, the production of a tire foresees an automated and substantially continuous process, in other words substantially without intermediate storage of semi-finished products. In such a process, a plurality of structural components of the tire made from elastomeric material not reinforced by cords (for example liner, under-liner, sidewalls, tread band, inserts made from elastomeric material, etc.) is manufactured, according to a predetermined sequence, from continuous elongated elements fed by a supplying member, for example a drawing plate/extruder, and then deposited on a forming support through a plurality of axially adjacent and/or radially overlapping coils, by means of at least one pressing member active on the continuous elongated element along a pressing direction.